In Patent Document 1, a kind of plasma processing method is described. In this plasma processing method, a MRAM device is manufactured by processing a multilayered object including a magnetic tunnel junction (MTJ) in which an insulating layer is interposed between a lower magnetic layer and an upper magnetic layer. In this method, Al2O3 is used as a material of the insulating layer. A magnetization direction of the lower magnetic layer is fixed, but a magnetization direction of the upper magnetic layer is changed by an external magnetic field. To be specific, in the method described in Patent Document 1, the MRAM device is manufactured by (a) forming a first mask on an upper electrode layer, (b) plasma-etching the upper electrode layer, the upper magnetic layer, and the insulating layer, (c) removing the first mask, (d) forming a second mask on the upper electrode layer, and (e) etching a lower electrode layer.